<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    div {
      transform: rotate();
    }
  </style>
</head>

<body>
  <div id="app">
    {{arr}} ==== {{total}}
  <input type="text" v-model.number="val" @keyup.enter="jin">
  </div>
  <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.7.14/vue.min.js"></script>
  <script>
    const an = new Vue({
      el: '#app',
      data: {
        arr:[1,2,3,4,5],
        val:''
      },
      methods: {
      jin(){
        this.arr.push(this.val)
        this.val=''
      }
      },
      computed:{
      total(){
        return this.arr.reduce((sum,item)=> sum+item,0)
      }
      }
    })
  </script>
</body>

</html>